The present invention generally relates to golf clubs and, more particularly, to a golf club having a head with a combination of improved perimeter weighting characteristics, vibration damping characteristics and increased striking face surface area.
The individual golf club heads in a set typically increase progressively in strike face surface area and weight as the clubs progress from the long irons to the short irons. Therefore, the club heads of the long irons have a smaller strike face surface area than the short irons and are typically more difficult for the average golfer to hit consistently well. For conventional club heads, this arises at least in part due to the smaller sweet spot of the corresponding smaller strike face.
To help the average golfer consistently hit the sweet spot of a club head, many golf clubs are available having heads with so-called cavity back designs with increased perimeter weighting. Another trend has been to simply increase the overall size of the club heads, especially in the long irons. Each of these features will increase the size of the sweet spot and therefore make it more likely that a shot hit slightly off the center of gravity of the club head still makes contact with the sweet spot and flies farther and straighter as a result. One challenge for the golf club designer when maximizing the size of the club head concerns maintaining a desirable and effective overall weight of the golf club. For example, if the club head of a three iron is increased in size and weight, the club may become difficult for the average golfer to properly swing.
In recent years, the importance of acoustics and vibration characteristics of golf clubs has come to the fore, because both vibration and sound are determinative in the xe2x80x9cfeelxe2x80x9d of clubs due to the direct sensation of touch and the psycho-acoustic feedback associated with the sound. Most golfers prefer that golf clubs minimize levels of shock, vibration, and airborne noise. Shock and vibration are particularly important in determining performance and tactile sensation, while vibration and airborne noise are critical for impact and psycho-acoustic feedback to the golfer. For the average golfer, a significant sting (structure-borne vibration) on the hands frequently results from an off center (away from the xe2x80x9csweet spotxe2x80x9d) impact of the club head with the golf ball. Various types of vibration damping and/or acoustic attenuating inserts have been incorporated into club heads to absorb these impact vibrations and audible sounds. However, there is still a need for improvements in weight redistribution as well as vibration damping and/or acoustic attenuation in golf club heads, and especially in iron type club heads.
The present invention is directed to a golf club with improved vibration damping and/or acoustic attenuation, as well as weight distribution. The golf club comprises a shaft and a club head. The body portion of the club head has a front cavity in its front portion and a back cavity in its back portion. Two apertures, one upper and one lower, extend laterally across a substantial upper portion and a substantial lower portion of the body portion, respectively. The apertures also extend front-to-back through the body portion communicating with the front and back cavities. The front cavity serves to hold a strike face insert that makes direct contact with golf balls during play. Preferably, the strike face insert has a strength-to-weight ratio greater than that of the body portion. Optionally, a third cavity is disposed within the front cavity below the upper aperture. The third cavity also extends laterally across a substantial lower portion of the body portion, encompassing a recessed rim that surrounds an entire front portion of the lower aperture. The upper aperture, the lower aperture and the third cavity all serve in part for eliminating material and weight generally from central portions of the club head.
In one embodiment of the invention, a vibration damping and/or acoustic attenuating member occupies essentially the entire lower aperture and a portion of the back cavity. Alternatively, the vibration damping and/or acoustic attenuating member is flanged between the strike face insert and the recessed rim, thereby filling the entire third cavity, the entire lower aperture and a portion of the back cavity. The vibration damping and/or acoustic attenuating member preferably has a shear modulus of at least about 1 Mpa, more preferably at least about 2 MPa, and a loss factor of at least about 0.05, more preferably at least about 0.1, over a temperature range of from about 10xc2x0 C. to about 40xc2x0 C. and a frequency range of from about 50 Hz to about 5000 Hz, over a temperature range of from about 10xc2x0 C. to about 40xc2x0 C. and a frequency range of from about 50 Hz to about 5000 Hz.
Suitable materials to form the vibration damping and/or acoustic attenuating member include without limitation viscoelastic elastomers; vinyl copolymers with or without inorganic fillers; polyvinyl acetate with or without mineral fillers such as barium sulfate; acrylics; polyesters; polyurethanes; polyethers; polyamides; polybutadienes; polystyrenes; polyisoprenes; polyethylenes; polyolefins; styrene/isoprene block copolymers; metallized polyesters; metallized acrylics; epoxies; epoxy and graphite composites; natural and synthetic rubbers; piezoelectric ceramics; thermoset and thermoplastic rubbers; foamed polymers; ionomers; low-density fiber glass; bitumen; air bladders; liquid bladders; acoustic absorbing materials; Helmholtz resonators; and mixtures thereof. Alternatively, the vibration damping material may be a low-density granular material including perlite; vermiculite; polyethylene beads; glass microspheres; expanded polystyrene; nylon flock; ceramics; polymeric elastomers; rubbers; dendritic particles; or a mixture thereof.
In another embodiment of the invention, the vibration damping and/or acoustic attenuating member may comprise a plurality of layers and a plurality of materials.
In an alternative embodiment of the invention, the vibration damping and/or acoustic attenuating member further contains a weight member that has a specific gravity greater than that of the body portion.
In a further embodiment, an indicia is scribed on a back surface of the vibration damping and/or acoustic attenuating member, so that it is visibly displayed in the back cavity.
In a particular embodiment of the present invention, a golf club of the iron type with improved vibration damping and weight distribution comprises a shaft and a head having a body. The body comprises a back cavity, a front cavity containing a strike face insert, and third cavity within the front cavity. The strike face insert has a strength-to-weight ratio greater than that of the body. An upper aperture is disposed front-to-back through the body connecting the front and back cavities and adjacent to the strike face insert. A lower aperture is disposed front-to-back through the body connecting the third and back cavities. A vibration damping and/or acoustic attenuating member is disposed immediately adjacent to a rear surface of the strike face insert, occupying the entire third cavity, the entire lower aperture and a portion of the back cavity.
The present invention is also directed to a set of golf clubs comprising a plurality of clubs, each having a club head and a shaft that is shorter in length than the shaft of a preceding club in the set. Each club head of the plurality of clubs comprises a front portion having a front cavity and a back portion having a back cavity. The front cavity has a third cavity formed within. The back cavity connects with the front cavity through an upper aperture, and it connects with the third cavity through a lower aperture. A strike face insert is attached within the front cavity.
In one embodiment, the strike face insert is progressively larger for at least some clubs in the set.
In another embodiment, each of the plurality of club heads has a vibration dampening and/or acoustic attenuating member occupying the entire third cavity, the entire lower aperture and a portion of the back cavity. Optionally, the vibration damping and/or acoustic attenuating member comprises a plurality of layers and a plurality of materials.
In a further embodiment of the invention, the vertical position of a center of gravity of the club head progressively elevates for at least some clubs in the set. This may be achieved by progressively decreasing the vertical positions of the upper aperture, the lower aperture and/or the third cavity for at least some clubs in the set.
In order to increase the club head weights from longer irons to shorter irons, the volume of material of a shelf surrounding the upper aperture and the volume of material of a rim surrounding the lower aperture may progressively increase for at least some clubs in the set. Alternatively or in combination, the volumes of the upper aperture, the lower aperture, and/or the third cavity may progressively decrease for at least some clubs in the set.
The increasing trend in weight within the set of clubs may also be achieved by progressively increasing the weight of the vibration damping and/or acoustic attenuating member for at least some clubs in the set, either by using materials of increasing density, or by increasing the volume of the member.
In another embodiment of the present invention, the vibration damping and/or acoustic attenuating member further contains a weight member. With this embodiment, trends of increasing weights and increasing vertical positions of centers of gravity may be realized by progressively increasing the volume, the density and/or the vertical position of the weight member for at least some clubs in the set.